[PATCH] D128619: [Clang] Implement P0848 (Conditionally Trivial Special Member Functions)

[Barry Revzin via Phabricator via cfe-commits]

BRevzin added inline comments.


================
Comment at: clang/test/AST/conditionally-trivial-smfs.cpp:39
+
+template struct DefaultConstructorCheck<2>;
+// CHECK:             "kind": "ClassTemplateSpecializationDecl",
----------------
royjacobson wrote:
> BRevzin wrote:
> > It's possible that I just don't understand what these tests actually mean but... where is the test for `DefaultConstructorCheck<2>` having a deleted default constructor, or `DefaultConstructorCheck<3>` having a non-defaulted one?
> > 
> > It'd also be worthwhile to have at least one test with constaints that subsume each other instead of being mutually exclusive. 
> Should I check this? Except destructors, the other SMFs are found during overload resolution using the usual lookup that already takes into account delete/default/constraints etc.
> 
> This patch is about making sure that we set the triviality attributes correctly according to the eligible functions, so this is what I added tests for.
> 
> Most of this testing is done in the sema test, but I need this AST test as well to make sure we get the `canPassInRegisters` attribute correctly - we're doing some custom processing over the functions without the usual type attributes because there are some weird compatibility edge cases.
> 
One of the motivations for the paper is to ensure that like given:

```
template <class T>
struct optional {
    optional(optional const&) requires copyable<T> && trivially_copyableT> = default;
    optional(optional const&) requires copyable<T>;
};
```

`optional<string>` is copyable (but not trivially copyable), `optional<int>` is trivially copyable, and `optional<unique_ptr<int>>` isn't copyable. I'm not sure what in here checks if that works. 


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D128619/new/

https://reviews.llvm.org/D128619